1. Field of the Invention
The present invention generally relates to medical devices, and more particularly, relates to guide wires and coils with radiopaque markings. Specifically, the present invention pertains to a radiopaque wire in a guide wire to provide visibility of the guide wire.
2. Description of the Prior Art
The desirability of using coils of wire for spring guide wires to provide structural integrity for and improve the handling characteristics of guide wires and catheters is known. Usually these devices are designed to traverse a finite distance within the body of the patient and within the vascular system, urethra, or other passageway of the patient.
The coil spring may run the entire length of the medical device or be appended in a particular region, such as the distal end.
Most spring guide wires are wound as single filar coils. U.S. patent application Ser. No. 07/384,398, filed on Jul. 24, 1989, entitled "Hollow Lumen Cable Apparatus" by Fleischhacker et al., describes multifilar spring guide wires. While the multifilar spring guide wires may be more expensive to implement, the multifilar spring guide wires are perceived to have superior handling characteristics.
It is very desirable to mark positions along the length of the device to more accurately position the device within the patient's body under fluoroscopy. This is usually accomplished through the use of a platinum or platinum alloy coil.
U.S. Pat. No. 4,538,622 issued to Samson et al., and U.S. Pat. No. 4,545,390 issued to Leary each employ a separate coil of a radiopaque material. However, placement of a marker using these approaches tends to undesirably add to cost, either in the form of excessive use of the platinum alloy and/or the necessary addition of tedious assembly steps.
In some cases, it may be advantageous to visualize the entire coil length of a guide wire under fluoroscopy so as to see the guide wire track in the vasculature. It may also be desirable to mark just the distal tip section of the guide wire or other predetermined points of the guide wire as deemed necessary.
The prior art devices do not provide a solution to both problems. If a guide wire is designed with a coil which is entirely radiopaque, one cannot easily see other device markers passing over it, but the guide wire coil can be easily seen over its entire length.
The present invention overcomes the disadvantages of the prior art spring guide wires by providing a technique for radiopaque marking which is both flexible and easily implemented while at the same time having minimum or negligible impact on the handling characteristics of the resulting device. The device can be manufactured to provide a soft trace of radiopacity in the main body of the coil so it can be visualize yet not obscure other markers riding over it, and in the same coil provide a pronounced radiopaque tip for accurate placement.